The present invention provides an improvement to what is commonly known as a universal joint, a Hooke's joint or a Cardan's joint. All of these joints provide what is known as a kinematic linkage between an input shaft and an output shaft. The kinematic linkage transfers rotational movement of the input shaft to the output shaft. The kinematic linkage provided by these joints can be used to connect two shafts that have an angular misalignment. In other words, the connection between the input and output shaft may be straight or at an angle.
Universal joints, however, do not provide speed reduction across the joint. A separate gear system is required in order to reduce the input rotational velocity if a lower output rotational velocity (and higher output torque) is desired.
Numerous attempts at improving on the general universal joint concept have been made. These attempts include U.S. Pat. No. 2,235,427 to Harris which discloses a pivotally adjustable universal joint, U.S. Pat. Nos. 4,509,932 to Weible and 4,352,276 to Smith which teach universal joints with improved centering members or devices to provide constant output velocity and U.S. Pat. Nos. 4,103,513 to Grosser, 3,036,446 to Morgenstern and 3,260,070 to Preston disclose rolling-contact universal joints for transmitting power from one shaft to another. None of these references, however, disclose an improved universal joint which combines the kinematic linkage of two misaligned shafts (i.e. a universal joint) with speed reduction.
Thus, there is a need for an improved universal joint that enables pivotal movement between the input and output shafts and further providing speed reduction between the input and output shafts. The output shaft angular velocity should preferably be a fraction of the input shaft velocity and the ratio of the input shaft velocity to output shaft velocity should be a function of the structural design of the joint. Such a joint would have significant and broad applications in mechanical power transmission equipment including, but not limited to automotive power transmission componentry such as drive axles, gear boxes, drive hubs, drive shafts and steering systems. The improved joint would save space because it would combine two functions, i.e. pivotal kinematic linkage and gear reduction, that previously required two separate systems, i.e. a universal joint linked to a speed reduction gear system.